Question DSMB Question

[aangaroo]

Hi,

I've been working on improving my skill with DSMB deployment and have a question about weighting.

I have the big DGX DSMB and it requires probably two maybe even three full breaths before releasing at safety stop depth at about 15 ft. I have trouble staying down during my second breath and I need barely any air in my wing at that depth so I don't have anything to dump.

I practice in a pool at my LDS and last time I was testing my semidry and used 14 lbs and I had a lot of trouble sinking the first couple feet from the surface. A very slow descent but had no trouble staying down once past the first few feet. This leads me to think I'm actually properly weighted.

Would it be a good idea to maybe increase weight to 16 lbs so I have a little more leeway when deploying my DSMB?

 

[Rob9876]

Personally I never deploy the DSMB that shallow -- I tend to shoot it around 30 or 40 feet, sometimes deeper, and usually just with 1 breath.

Sounds like you're deploying shallow because of pool limitations? If so, I'd be inclined to just accept the fact that for training you're not going to get the DSMB full -- rather than change your weighting if you are otherwise fine holding your safety stop.

But if you want/need to fully inflate at 15 feet, then I would increase your weights -- no need to risk popping up from 15 feet (which can still be dangerous).

 

[inquis]

I would not add weight to allow multiple breaths. Either get a smaller one for pool training or just accept that it won't be full.

One option that you may see is to use an inflator hose. I'm not a fan of that approach, since you're pretty committed. Once started, there is no good way to delay release if the need raises (e.g., entanglement or someone swims above you).

 

[aangaroo]

Another question: You're supposed to look up before releasing your DSMB but what if visibility is poor?

 

[Rob9876]

Another question: You're supposed to look up before releasing your DSMB but what if visibility is poor?

Look up anyhow. Even if you can't see the surface, you'll want to make sure another diver has not silently gotten right above you.

 

[Edward3c]

Hi,

I've been working on improving my skill with DSMB deployment and have a question about weighting.

I have the big DGX DSMB and it requires probably two maybe even three full breaths before releasing at safety stop depth at about 15 ft. I have trouble staying down during my second breath and I need barely any air in my wing at that depth so I don't have anything to dump.

I practice in a pool at my LDS and last time I was testing my semidry and used 14 lbs and I had a lot of trouble sinking the first couple feet from the surface. A very slow descent but had no trouble staying down once past the first few feet. This leads me to think I'm actually properly weighted.

Would it be a good idea to maybe increase weight to 16 lbs so I have a little more leeway when deploying my DSMB?

Remember every Lt of air you put into your DSMB gives it 1kg of lift. Rather than increase the weight you’re carrying (which will increase air consumption) deploy the DSMB from a deeper depth. I normally have launched mine at 10m or deeper.

 

[BRT]

A 6' DSMB might have 40 lb of lift if full. To deploy it at 10 meters and have it full at the surface you would have to fill it half full. 20 lb of lift. Not going to happen. I like to have a big DSMB because it is a backup flotation device. Since I don't want to carry two, I accept that it is just a bright thing that floats flat on the surface.

 

[Matt B]

I agree that deploying deeper is the way to go. If you are on a dive, when you reach safety stop depth, your tank is nearly empty making you even more buoyant.

 

[divingdayz]

Deploy it deeper. It's safer and elimates your problems. Happy bubbles.

 

[Badger7]

I have the big DGX DSMB and it requires probably two maybe even three full breaths before releasing at safety stop depth at about 15 ft. I have trouble staying down during my second breath and I need barely any air in my wing at that depth so I don't have anything to dump.

I think I have the same DSMB. Even though it's FAR easier to release it with a single breath at greater depth, I wanted to practice and get it working well at 12-15' in a pool. I had some free time while a DM I was practicing with was helping an OW class, so I played with it for about an hour while practicing keeping trim, sticking to depth, and getting a decent deploy at a shallow safety stop depth.

What finally worked pretty good for me was relaxing and focusing on breath control. What I would do is first chill, find some zen, dump most of my wing, and take a very large breath to completely full lungs, and then only breath out to about half full lungs, then repeat back to totally full. I made minor adjustments to wing inflation until I was absolutely neutrally buoyant, nearly motionless, and resumed that breath pattern for a while to make absolutely sure, just to get the really good feel for breathing slowly with very full lungs to about half full lungs.

Then I put a small puff of air in my dsmb to get it to unfurl, made sure I was chill with the spool and the line, and then when I was at the top of a breath, with 100% full lungs, I would breath out almost the full set of lungs into the dsmb, very chill, no hurry, no stress. When I put my reg back my cakehole to take another breath, I only breathed up to about half full. Didn't suck in a big lung full, just enough to keep a normal breathing pattern but shallow and low volume. Then I stopped filling the dsmb for a hot minute. I took time to make sure bouyancy was still stable (not messing with the inflator, just verifying I'm still hovering), controlled breathing between half full lungs and empty lungs. Not going anywhere, still neutrally bouyant, less gas in the lungs to offset the extra gas in the dsmb. Taking another breath up to about 75%, and you'll see yourself start to rise a just a little, dump that entire breath into the dsmb, and let it unspool and pop to the surface. Then I just put the reg back in my mouth and resumed breathing between about half full and totally full.

It wasn't perfect, but it worked pretty well and I had a big fully inflated SMB at the surface without an unplanned ascent. I'll play around with it some more in the quarry this spring at 15', will try it by just watching the depth gauge on my computer without the wall of the pool to work from.